Pete Blackshaw was so excited about getting a hybrid gasoline-electric car that he had his wife videotape the trip to the Honda dealership to pick up his Civic Hybrid. The enthusiastic owner ordered a customized license plate with "MO MILES" on it, and started a blog about his new hybrid lifestyle.

But after a few months of commuting to his job in Cincinnati, Blackshaw's hybrid euphoria vanished as his car's odometer revealed that the gas mileage he was hoping for was only a pipe dream. Honda's Civic Hybrid is rated by the EPA to get 47 miles per gallon in the city, and 48 mpg on the highway. After nearly 1,000 miles of mostly city driving, Blackshaw was getting 31.4 mpg.

"I feel like a complete fraud driving around Cincinnati with a license plate that says MO MILES," says Blackshaw, who claims that after 4,000 miles his car has never gotten more than 33 mpg on any trip. The tenor of Blackshaw's blog shifted from adulation to frustration after his Honda dealer confirmed that his car was functioning properly, and that there was nothing he could do.

Blackshaw, who is chief customer satisfaction officer at Intelliseek.com, spoke to a Honda regional manager about his concerns, and wrote a letter to a Honda vice president on April 15 that was not answered. His story has been echoed dozens of times online by owners of the Honda Civic Hybrid and Toyota Prius.

Drivers rarely see the actual EPA-rated mileage in the real world, according to John DiPietro, road-test editor of automotive website Edmunds.com. DiPietro says most drivers will get between 75 to 87 percent of the rated mileage, with individual variations based on driving habits and traffic route. "If a new car gets less than 75 percent of its EPA rating, then it should be retested."

Data from independent product-testing organization Consumer Reports indicates that hybrid cars get less than 60 percent of EPA estimates while navigating city streets. In Consumer Reports' real-world driving test, the Civic Hybrid averaged 26 mpg in the city, while the Toyota Prius averaged 35 mpg, much less than their respective EPA estimates of 47 and 60 mpg. Hybrid cars performed much closer to EPA estimates in Consumer Reports' highway tests.

Consumer Reports' senior auto test engineer Gabriel Shenhar says that while the EPA test is a lab simulation, Consumer Reports puts the cars on the streets and measures the fuel consumed to more accurately reflect gas mileage.

The 19-year-old EPA tests for city and highway mileage actually gauge vehicle emissions and use that data to derive an estimated fuel-efficiency rating. The EPA tests pre-production vehicles in a lab to simulate vehicle starts and stops on crowded city streets and open road conditions. According to the EPA website, "The tests measure the waste substances emitted from consuming the fuel, not the actual fuel consumed. From the measurement of emissions, EPA can estimate the miles per gallon achieved by the vehicle on average."

"The (EPA) test needs to include more fundamental engineering," says John H. Johnson, an automotive expert who co-authored a 2002 National Academy of Sciences report on fuel-efficiency standards. "They haven't been updated to encompass hybrids."